The present invention relates to a method of incorporating photographically useful compounds into a hydrophilic colloid layer of an imaging element, to self-assembled compositions of silver halide and photographically useful compounds, and to radiation sensitive imaging elements containing such self-assembled compositions incorporated therein.
Substances necessary for obtaining a photographic image or compounds for obtaining a photographic image of higher quality are called photographically useful compounds. The photographic process, in its most basic form, is comprised of silver halide (capable of detecting light and storing it as latent image) and developer molecules (capable of converting the latent image to a visible image). These two chemistries, however, are incompatible, as unexposed silver halide is thermodynamically unstable with respect to reduction in the presence of developer molecules. Silver halide may also be unstable with respect to other additional photographically useful compound chemistries, which we will refer to using the term xe2x80x9cactive chemistryxe2x80x9d. Examples of other potentially active chemistries in addition to developing agents include auxiliary developing agents, development accelerators, dyes, fogging agents, silver halide solvents, couplers, compounds which accelerate coupling reaction of couplers, bleaching accelerators, fixing accelerators and development inhibitors. The consequence of this is that many photographic components must be kept separate, each function performed in sequence and thus, modern photography requires multiple steps: exposure and processing.
Incorporation of active chemistry directly into film formulations, to either simplify or improve processing after exposure, has long been a goal in the photographic industry. Some photographically useful compounds are difficult to incorporate in a stable fashion into a light-sensitive material, however, or cause serious deterioration in the photographic capability if incorporated. These compounds, if incorporated directly into the photographic elements, typically need to be stabilized or rendered harmless by chemical modification prior to photographic processing. Methods of incorporating development and other active chemistries into photographic element formulations have been described in a number of patents and publications. Schleigh and Faul, in Research Disclosure 129 (1975) describe methods of appending color developers with xe2x80x9cblockingxe2x80x9d chemistry to prevent premature reaction. U.S. Pat. No. 6,261,757 to Irving et al. describes photographic articles in which developers and other photographic chemistries are ionically bound to the surface of ion-exchange resins. In each of these methods, including the conventional photographic process, silver halide and active chemistry are physically separated (by distances on the order of microns, or much more), such that diffusing or mixing the two together requires the application of a relatively large amount of energy, e.g., in the form of chemical solutions or heat. However, in such prior art methods imaging elements obtained are still frequently subject to poor keeping characteristics.
It would be desirable to provide alternative methods for obtaining an imaging element with active chemistry photographically useful compounds directly incorporated therein, which exhibits good photographic performance as well as excellent keeping characteristics. It would be further desirable to provide materials capable of detecting imagewise scattered actinic radiation, storing the detected image as latent image, and further capable of developing said latent image to obtain an image. Accordingly, it would be desirable to provide a methodology whereby incorporated active chemistry in an imaging element may be xe2x80x9cswitched offxe2x80x9d, and thus rendered inert, and later xe2x80x9cswitched onxe2x80x9d to perform a desired function.
In accordance with one embodiment of the invention, a radiation sensitive imaging element is described comprising a support bearing one or more hydrophilic colloid layers, wherein a photographically useful compound is incorporated into at least one hydrophilic colloid layer in the form of a self-assembled composition comprising a substantially homogeneous and ordered array of the photographically useful compound and silver and halide atoms, wherein the average minimum distance from each Ag atom in the composition to an atom of the photographically useful compound in the composition is less than 50 xc3x85. In a particular embodiment, the self-assembled composition is of the general unit cell formula
AgaXb(PUC*)c.nH2O
where X represents halogen atoms selected from Cl, Br, and I or any combination thereof, and PUC* is a photographically useful compound containing at least one positively charged onium ion group; and wherein a is an integer from 1-10 and b is an integer from 2-18, with the proviso b is greater than a, and the silver and halide atoms form silver halide sublattice structures having a net negative charge; c is an integer such that the onium ion group containing photographically useful compound forms a positively-charged sublattice which stabilizes the negatively charged silver halide sublattice, wherein charge neutrality for the composition is upheld; and n is any rational number from 0 to 10. Further embodiments of the invention are directed towards self-assembled compositions of silver halide and photographically useful compounds as described, as well as to a method for preparing a radiation sensitive imaging element, comprising forming the self-assembled compositions, adding the self-assembled composition to a hydrophilic colloid layer coating composition, and coating the hydrophilic colloid layer coating composition to form a layer of the imaging element.
The invention provides novel materials and a method of incorporating active chemistry compounds such as developers or development inhibitors directly into a photographic imaging element. The invention further provides materials, and a method for preparing materials, comprising silver halide co-crystallized with photographic useful compound molecules thereby creating a unique crystal lattice. The invention described herein provides materials in which active chemistry and silver halide are present together in an ordered array, or crystal lattice, separated by distances measured on the atomic scale (i.e., in angstroms (xc3x85), where 1 xc3x85=10xe2x88x924 xcexcm).